[unreadable] The goal of this Phase II proposal is to complete the development and demonstration of a novel gradient coil suitable for human head Magnetic Resonance Imaging (MRI) at fields from 1 to 8 T with substantially higher performance than is currently available. The coil will be capable of continuous field gradients in excess of 80 mT/m on all axes with slew rates up to 400 T/m/s at improved efficiency. The gradient coil will be switchable between a configuration optimized for functional MRI (fMRI) using Echo Planar Imaging (EPI) and one optimized for high-gradient techniques such as high-resolution diffusion-weighted microscopy MRI (DWI). Compared to state-of-the-art head gradient coils, the novel force-canceled "crescent" gradient coil will have twice the continuous gradient capability, 25 Db less acoustic noise, and reduced nerve stimulation at higher slew rates. The coil will enable a substantial improvement in image resolution and/or imaging time on MRI scanners by all manufacturers. DWI, fMRI, and ultra-fast 3D gradient-echo angiography techniques will become widely practical. DWI has shown promise in the detection of acute ischemia within minutes (hours before it is seen in T2-weighted images); and ultra-high-field DWI has demonstrated order-of-magnitude advantages in resolution in white matter and nerves, owing to the diffusion anisotropy of the myelin. High-field DW EPI permits complete brain scans in under 0.1 second with adequate resolution for real-time monitoring of brain function, but it is not currently generally practicable because of gradient coil limitations. [unreadable] [unreadable] The Phase I comparative simulations and analyses (electromagnetic, thermal, and acoustical) of virtually all known head gradient coil designs showed substantial advantages of the novel design. The head gradient coil was manufactured and assembled to permit preliminary bench testing and analysis, which confirmed the feasibility and manufacturability of the novel coil design. All of the Phase I objectives were met or exceeded. [unreadable] [unreadable] The Phase II effort will demonstrate the performance of the gradient coil in imaging experiments in a 3 T Siemens whole-body magnet at Massachusetts General Hospital (MGH) in collaboration with Dr. Jerome Ackerman (Harvard Medical School) and complete the product development and optimization. Early in the Phase II, the coil completed during Phase I will be field-tested. A second-generation head gradient coil, primarily with improved manufacturability, will then be constructed and tested. The FDA approval process will be initiated near the end of Phase II, and marketing, manufacturing, and licensing discussions will be pursued with Siemens, GE Medical Systems, Magnex, and perhaps others. [unreadable] [unreadable]